Among three layers of membranes (pia mater, arachnoid, and dura mater) for protecting cerebral parenchyma in a cranial bone, the dura mater is the hardest outermost layer and is also the inner periosteum of the cranial bone. In brain neurosurgery, excision of the dura mater is often unavoidable, and this causes a defect in the dura mater. Spontaneous contraction of the dura mater itself sometimes complicates primary suturing. Occlusion of wound while the dura mater remains open results in serious complications, for example, intracranial infection caused by leakage of spinal fluid, local neurological symptom caused by adhesion between cerebral parenchyma and bones or subcutaneous tissues, and a focus of epileptic seizure. Therefore, when a wound is occluded, precise suturing is required in order not to create a gap in the dura mater. When a defect appears in the dura mater, or primary suturing is difficult, some prosthesis should be used to completely suture without any gap.
Selection of a prosthesis for use in filling a dura mater defect is a problem which has troubled neurosurgeons for a long time. At an early stage, artifacts were used, however, there were problems such as biocompatibility and usability. Thus, no artifact has been used for a long period. Autogenous fascia is the most extensively used prosthesis from the early stage up to the present, but problems associated with autoaenous fascia include production of fascia defect on the extracted region and easy adhesion to the brain. A human dried dura mater is a prosthesis for the dura mater prepared by treating the dura mater collected from a corpse with radiation, and has been the best prosthesis among existing ones. However, prions which may be a cause of Creutzfeldt Jakob disease, are potentially present in the dura mater, and infection of Creutzfeldt Jakob disease through a human dried dura mater has been reported. Therefore, use thereof was completely prohibited in 1998.
The only material usable as a prosthesis for the dura mater in addition to autogenous fascia is ePTFE (expanded polytetrafluoroethylene), which has been approved by Department of Health and Human Services. Because ePTFE is a polymeric material, it has no adhesiveness to organisms. This property is excellent in that ePTFE does not adhere to the brain. On the other hand, ePTFE is poor in contractility, and spinal fluid can leak from a pinhole, thereby requiring suturing with the use of special surgical suture. Since there is no adhesiveness to organisms, spinal fluid is highly likely to leak from a gap between suture surfaces. In addition, since there is no adhesiveness to peripheral tissue, it is highly likely to be no more than a skeletal material. Many attempts have been heretofore made on how to successfully use ePTFE. However, all of these attempts involved using ePTFE as a skeletal material and waiting until a coat of fibrous tissue was formed on the periphery.